Georges Island was farmland until the United States Military bought it in 1825 in order to fortify the coastal defenses. When first built, Fort Warren was a modern fort with a searchlight station, magazines for gun powder, a hospital wing, and a prison. The fort was dedicated in 1847. During the Civil War, it was used as a training ground and prison, famous for humane treatment of Confederate prisoners.

In 1947, the fort was decommissioned for military use, and in 1958, the Massachusetts Department of Conservation and Recreation began preservation efforts.

The grounds are completely open to visitors (via a park shuttle boat) - you can walk from the turrets to the dungeons and to the barracks. The Massachusetts Department of Conservation and Recreation added park amenities to the former fort: guided tours, picnic places with grills, walking trails, and even a snack station.

The Park is also a National Historic Landmark.